TOXIC GASES AS A CONTROL OF THE PEACH-TREE BORER. 
13 
previously determined larvicidal value. The one-half -ounce dose in 
many instances gave as perfect control as the next two larger doses, 
and in some cases better. On the whole, however, the results from 
the application of this dose are not quite so uniform and the general 
average is slightly less. As will be seen from the table, there is not 
a great difference in the control obtained from either the one-half- 
ounce, the three- fourths-ounce, or the 1-ounce doses. Apparently 
there is considerable latitude in the dosage required, within these 
limits, but it does not seem likely that much less than one-half -ounce 
doses would give consistent control. On the other hand, there does 
not seem to be much point in using doses larger than 1 ounce. 
Other experiments were carried on in which very much larger 
doses than those shown in Table VI were used, but in none of these 
was there an advantage in the control obtained sufficient to offset the 
probability of injury from the greatly prolonged fumigation. Table 
IV gives the results of one such experiment, made at Springfield 
in 1916. 
Table IV. — Effect of stated doses of para-dichlorobenzene on 8-year-old peach 
trees, Springfield, W. Va., 1916. 
Num- 
Dose per tree. 
Daje of— 
Interval 
in days 
from ap- 
plication 
to exam- 
ination. 
Number of active 
larvae. 
ber of 
trees. 
Applica- 
tion. 
Examin- 
ation. 
Total. 
Per 
tree. 
Injury. 
5 
June 24 
...do 
...do 
Aug. 22 
June 24 
...do 
...do 
...do 
Aug. 22 
June 24 
...do 
...do.... 
...do.... 
Aug. 22 
June 24 
...do.... 
...do.... 
...do.... 
Aug. 22 
June 24 
...do.... 
...do.... 
...do 
Oct. 14 
Oct. 27 
Oct. 28 
...do 
Oct. 14 
Oct. 18 
Oct. 27 
...do 
Oct. 28 
Oct. 14 
Oct. 18 
Oct. 28 
Oct. 27 
Oct. 28 
Oct. 14 
Oct. 27 
Oct. 28 
Oct. 27 
Oct. 28 
Oct. 14 
Oct. 27 
Oct. 28 
...do 
112 
125 
126 
67 
112 
116 
125 
125 
67 
112 
116 
126 
125 
67 
112 
125 
126 
125 
67 
112 
125 
126 
126 
67 
67 
67 
67 
29 
12 
3 
5.8 
2.4 
.6 
5 
5 
5 
do 
do 
do 
None. 
None. 
5 
9 
25 
15 
6 
1.8 
5.0 
3.0 
1.2 
5 
5 
5 
5 
do 
do 
do 
do 
None. 
None. 
None. 
5 
None (1 tree moderate). 
None. 
None. 
5 
5 
5 
do 
do 
do 
do 
3 
4 
.6 
.8 
5 
:::::::::::: 
5 
5 
do 
do 
do 
do 
:::::::: ::r.:::::::: 
5 
5 
5 
5 
None (1 tree severe). 
5 
do 
do 
do 
do 
5 
.. l.: 
5 
1 
5 
Aug. 22 
...do 
...do.... 
...do.... 
...do.... 
...do.... 
1 
2 
None (1 tree traces). 
2 
...do 
2 
...do 
None (1 tree traces). 
1 
Total number of trees treated, 126. 
A total of 126 eight-year-old trees were treated with various doses, 
ranging from one-half ounce to 10 ounces per tree. Part of the ap- 
plications were made June 24 and part August 22. The examination 
was made in October. Of the entire 126 trees, 56 which received 
